[Numpy-discussion] complex numbers

[Tim Hochberg]

David L Goldsmith wrote:
> PS:  The Python built in function (i.e., you don't even need numpy for 
> this) abs(x) is "vectorized" (i.e., accepts a (nested) sequence, incl. 
> numpy array, argument) and overloaded to give the modulus (i.e., 
> Pythagorean "length") of a complex number when such is its argument.
>   
This isn't quite right. The built in abs function looks for the special 
method __abs__. So, abs(x) is equivalent to x.__abs__(). Arrays supply 
an appropriate __abs__ method, lists do not. For example:

 >>> l = [1,2,3,4]
 >>> abs(l)
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
TypeError: bad operand type for abs()
 >>> a = numpy.arange(5)
 >>> abs(a)
array([0, 1, 2, 3, 4])


-tim
> DG
>
> Kenny Ortmann wrote:
>   
>> excuse my laziness for not looking this up, I googled it but could not find 
>> a solution.
>> matlab has a
>> isreal(array)
>> where if the array is full of real numbers the value returned is 1.
>> I'm translating matlab code and ran across
>>
>> if ~isreal(array)
>>     array = abs(array)
>>
>> Is there a way to check to see if a number is real or complex? and if so is 
>> there a way to extract the(a + ib) because the absolute value of a complex 
>> number is like the pythagorean therom on a and b?
>>
>> thanks for your help,
>> Kenny
>>
>>
>>
>> -------------------------------------------------------------------------
>> Take Surveys. Earn Cash. Influence the Future of IT
>> Join SourceForge.net's Techsay panel and you'll get the chance to share your
>> opinions on IT & business topics through brief surveys -- and earn cash
>> http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV
>> _______________________________________________
>> Numpy-discussion mailing list
>> Numpy-discussion at lists.sourceforge.net
>> https://lists.sourceforge.net/lists/listinfo/numpy-discussion
>>   
>>     
>
>
>